Method and Apparatus for Compensating Code Channel Power in a Transmitter

1. A method in a transmitter having an output comprising: determining a transmit power indicator; determining a set of digital gains as a function of the transmit power indicator; applying the set of digital gains to a corresponding set of code channels, the set of digital gains setting relative powers of the set of code channels and also compensating for non-linearities in the transmitter as a function of the transmit power indicator such that a desired relationship between channel powers of said set of channels after having been combined to produce the output is substantially achieved; combining the set of channels to produce the output.

2. The method according to claim 1 wherein determining the transmit power indicator comprises: determining a signal representative of a total transmit power.

3. The method according to claim 1 wherein determining the transmit power indicator comprises: determining a signal representative of a current total transmit power.

4. The method according to claim 1 wherein the desired relationship between channel powers comprises a specified relative power for each of the channels in the output.

5. The method according to claim 1 wherein determining a set of digital gains as a function of the transmit power indicator further comprises: for each of at least one channel: using a non-linear function that is a function of the transmit power indicator in generating a digital gain value for the current state and for the current transmit power of the respective channel.

6. The method according to claim 5 wherein using a non-linear function further comprises: using a curve-fitting operation to provide the non-linear function.

7. The method according to claim 1 wherein determining a set of digital gains as a function of the transmit power indicator further comprises: for each of at least one channel: maintaining a respective pre-set digital gain value for the channel for each of a plurality of states of the set of channels, and as a function of the transmit power indicator; determining and using a digital gain value for the current state and for the current transmit power of the at least one channel by interpolation of pre-set digital gain values.

8. The method according to claim 5 wherein each state comprises a selection of a particular set of code channels from a set of possible code channels, and a selection of at least one of an encoding format, a signal format, and a data rate for at least one of the set of particular code channels.

9. The method according to claim 5 wherein each state comprises at least one of: a selection of a particular set of code channels from an available set; a selection of a particular encoder format for at least one code channel; a selection of a particular signal format for at least one code channel; and a selection of a particular data rate for at least one code channel.

10. The method according to claim 1 wherein, for each of at least one of the code channels determining a digital gain of said set of digital gains comprises: determining a nominal digital gain for the code channel; determining a gain adjustment for the code channel as a function of the transmit power indicator; combining the nominal digital gain and the gain adjustment to produce the digital gain of said set of digital gains for the code channel.

11. The method according to claim 1 wherein the code channels are CDMA code channels.

12. A transmitter having an output and a transmit power indicator, the transmitter comprising: a plurality of code channel generators and/or code channel encoders; for each code channel generator and/or code channel encoder, a respective digital gain element; a compensation element adapted to apply a set of digital gains to the digital gain elements, the set of digital gains compensating for non-linearities in the transmitter as a function of the transmit power indicator such that a desired relationship between code channel powers of said set of code channels after having been combined to produce the output is substantially achieved.

13. The transmitter according to claim 12 wherein the compensation element comprises: a digital gain determiner for determining a digital gain value for a current state and for a current transmit power of each channel, by using a non-linear function that is a function of the transmit power indicator.

14. The transmitter according to claim 12 wherein the compensation element comprises: a memory containing for at least one code channel, a respective pre-set digital gain value for the code channel for each of a plurality of states of the set of code channels, and for at least one of: a plurality of discrete values of transmit power; and a plurality of ranges of transmit power; a digital gain determiner for determining a digital gain value for a current state and for a current transmit power using interpolation of pre-set digital gain values.

15. The transmitter according to claim 12 further comprising: a power control subsystem adapted to determine the transmit power.

16. A computer readable medium having computer readable instructions stored thereon for implementation by a computer processor for implementing a method comprising: determining a transmit power indicator; determining a set of digital gains as a function of the transmit power indicator; applying the set of digital gains to a corresponding set of code channels, the set of digital gains setting relative powers of a set of code channels and also compensating for non-linearities in a transmitter as a function of the transmit power indicator such that a desired relationship between channel powers of said set of channels after having been combined to produce the output is substantially achieved.

17. The computer readable medium according to claim 16 wherein the method step of determining a set of digital gains as a function of the transmit power indicator further comprises: for each of at least one channel: using a non-linear function that is a function of the transmit power indicator in generating a digital gain value for the current state and for the current transmit power of the respective channel.

18. The computer readable medium according to claim 17 wherein the method further comprises: using a curve-fitting operation to provide the non-linear function.

19. The computer readable medium according to claim 16 wherein the method step of determining a set of digital gains as a function of the transmit power indicator further comprises: for each of at least one channel: maintaining a respective pre-set digital gain value for the channel for each of a plurality of states of the set of channels, and as a function of the transmit power indicator; determining and using a digital gain value for the current state and for the current transmit power of the at least one channel by interpolation of pre-set digital gain values.

20. The computer readable medium according to claim 17 wherein each state comprises a selection of a particular set of code channels from a set of possible code channels, and a selection of at least one of an encoding format, a signal format, and a data rate for at least one of the set of particular code channels.

21. A computer readable medium according to claim 20 wherein, for each of at least one of the code channels determining a digital gain of said set of digital gains comprises: determining a nominal digital gain for the code channel; determining a gain adjustment for the code channel in response to the transmit power indicator; combining the nominal digital gain and the gain adjustment to produce the digital gain of said set of digital gains for the code channel.